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darkfi/proofs/sapling.pseudocode
2020-09-19 14:16:41 +02:00

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# :set syntax=sapvi
# :source ../scripts/sapvi.vim
const:
G_VCV: SubgroupPoint
G_VCR: SubgroupPoint
G_SPEND: SubgroupPoint
G_PROOF: SubgroupPoint
G_NOTE_COMMIT_R: SubgroupPoint
G_NULL: SubgroupPoint
CRH_IVK: Blake2sPersonalization
NOTE_COMMIT: PedersenPersonalization
MERKLE: list<PedersenPersonalization>
PRF_NF: Blake2sPersonalization
contract input_spend(
value: U64 -> BinaryNumber
randomness: Fr -> BinaryNumber
ak: Point
ar: Fr -> BinaryNumber
nsk: Fr -> BinaryNumber
g_d: Point
commitment_randomness: Fr -> BinaryNumber
auth_path: [(Scalar, Bool)]
anchor: Scalar
) -> (Point, Point, Scalar, BinaryNumber):
let rk: Point = ak + ar * G_SPEND
emit rk
let nk: Point = nsk * G_PROOF
let mut ivk_preimage: BinaryNumber = []
ivk_preimage.put(ak)
let mut nf_preimage: BinaryNumber = []
ivk_preimage.put(nk)
nf_preimage.put(nk)
assert ivk_preimage.len() == 512
assert nf_preimage.len() == 256
let mut ivk = blake2s(ivk_preimage, CRH_IVK)
ivk.truncate(JUBJUB_FR_CAPACITY)
# This will error if ivk.len() != 256
#let ivk: Fr = ivk as Fr
let pk_d: Point = ivk * g_d
let cv: Point = value * G_VCV + rcv * G_VCR
emit cv
let mut note_contents: BinaryNumber = []
note_contents.put(value)
note_contents.put(g_d)
note_contents.put(p_k)
assert note_contents.len() == 64 + 256 + 256
let mut cm = pedersen_hash(note_contents, NOTE_COMMIT)
cm += commitment_randomness * G_NOTE_COMMIT_R
let mut position = []
let mut cur: Scalar = cm.u
for i in range(auth_path.size()):
let (node: Scalar, is_right: Bool) = auth_path[i]
position.push(is_right)
# Scalar -> AllocatedNum
let (left: Scalar, right: Scalar) = swap_if(is_right, cur, node)
let mut preimage: BinaryNumber = []
preimage.put(left)
preimage.put(right)
cur = pedersen_hash(MERKLE_TREE[i], preimage).u
enforce cur == rt
emit rt
let rho: Point = rho + position * G_NULL
nf_preimage.put(rho)
assert nf_preimage.len() == 512
let nf: BinaryNumber = blake2s(nf_preimage, PRF_NF)
emit nf
contract output_mint(
value: U64 -> BinaryNumber
randomness: Fr -> BinaryNumber
g_d: Point
esk: Fr -> BinaryNumber
pk_d: Point
commitment_randomness: Fr -> BinaryNumber
) -> (Point, Point, Scalar):
let cv: Point = value * G_VCV + rcv * G_VCR
emit cv
let mut note_contents: Binary = []
note_contents.put(value)
let epk: Point = esk * g_d
emit epk
let v_contents: Scalar = pk_d.v
let sign_bit: Bool = pk_d.u.is_odd()
note_contents.put(v_contents)
note_contents.put(sign_bit)
assert len(note_contents) == 64 + 256 + 256
let mut cm: Point = pedersen_hash(note_contents, NOTE_COMMIT)
let rcm: Point = commitment_randomness * G_NOTE_COMMIT_R
cm += rcm
let cmu: Scalar = cm.u
emit cmu